Selected compounds containing carbonyl groups and aliphatic unsaturation as anti-rads



United States Patent F SELECTED COMPOUNDS CONTAINING CARBON- YL GROUPS AND ALIPHATIC UNSATURATION AS ANTI-RADS Herbert R. Anderson, Jr., Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed June 16, 1960, Ser. No. 36,480 Claims. (Cl. 26045.85)

This invention relates to rubber products resistant to radiation damage.

The word rubber as used herein includes both natural and synthetic rubbery materials.

Rubber vulcanizates, when subjected to ionizing radiation, undergo deterioration in stress-strain properties, this being due to chain scission and cross linking. For instance, when sorne vulcanizates are subjected to radiation,

.such as alpha rays, beta rays, gamma rays, or neutrons,

there is a considerable increase in the modulus of the product, and the number of network chains, related to cross links, is increased. Other vulcanizates, when subjected to the same radiation, are degraded to softer and even liquid products. Such changes are undesirable in either case because the physical properties of the rubber are harmed by this radiation.

Some research has been done to determine what additives can be incorporated in the rubber to produce products which are resistant to radiation or at least more resistant than the material Without the use of such additives. These additives are referred to as radiation damage inhibitors or anti-rads. I have discovered a group of compounds which are very effective in reducing this deterioration or radiation damage. Broadly speaking, these organic compounds contain carbonyl groups and have aliphatic unsaturation. Thus, my invention resides in a method comprising incorporating in rubber certain organic compounds, all defined further hereinafter, to render said rubber resistant to radiation damage.

An object of my invention is to provide rubber vulcanizates which are resistant to radiation damage. A further object of my invention is to provide compositions containing certain additives which make the product exhibit less change in modulus than the same product Without the additive. A further object of this invention is to provide a method of reducing damage to rubber when subjected to ionizing radiation.

Other objects and advantages of my invention will become apparent to one skilled in the art upon reading the disclosure, and appended claims.

Thus, according to my invention, there is provided a method comprising incorporating in rubber, during the compounding thereof, a compound having the formulas 0 0' o R O R) H H 1"- 7 2 and RiCRsC-R1 Wherein: each R is selected from the group consisting of aromatic and substituted aromatic nuclei containing from 6 to 20 carbon atoms; each R is an alkenyl radical containing from 2 to 6 carbon atoms; and R is an alkenylene radical containing from 2 to 6 carbon atoms.

Further, according to the invention, there is provided a method of inhibiting a rubber from damage which is caused by exposure to ionizing radiation which method comprises incorporating into said rubber, as a radiation damage inhibitor, at least one of the above-identified organic compounds represented by Formulas I and II.

In the above Formulas I and II, the aromatic nuclei 3,250,740 Patented May 10, 1966 can contain as substituents such radicals as alkyl, amino, carboxy, and acyl. However, nitro and halogen substituents are to be avoided, as these groups promote damage due to ionizing radiation. The term aromatic nuclei is intended to includethe benzene nucleus, the naphthalene nucleus, and the biphenyl nucleus. Larger aromatic nuclei such as anthracene and phenanthrene are not to be included, since such large rings are not as effective in preventing the deterioration caused by ionizing radiation. Thus, with a 20carbon upper limit on the substituted aromatic nuclei, the aromatic nuclei can contain from 8 to 14 carbon atoms in substituent groups.

Examples of the selected organic compounds containing carbonyl groups and having aliphatic unsaturation, which can be used in the practice of this invention include, among others:

diallyl phthalate, divinyl-3-n-butylbenzene-1,2-dicarboxylate, di 3-butenyl -5-aminonaphthalene-1,2-dicarboxylate, di(4-hexenyl) 4-amino-5,6-di-n-pentylnaphthalene-1,3-dicarboxylate, diallyl 3-phenylbenzene-1,2-dicarboxylate, di(Z-butenyl) 4-acetylbenzene-1,2-dicarboxylate, diallyl S-carboxyl-6-acetylbenzene-1,4-dicarboxylate, trans-l,4-diphenyl-2-butene-1,4-dione, cis-1,4-dinaphthyl-2-butene-1,4-dione, cis-1,5-di(3-aminophenyl)-2-pentene-1,5-dione, trans-1,6-di(4-p-tolylphenyl)-3-hexene-1,6-dione, cis-l,4-di( 3-amino-4-tetradecylphenyl) -2-butene-1,4-

dione, and trans-1,6-di(S-amino-6-sec-decylnaphthyl)-2-octene-l,8-

dione.

The amount of any radiation inhibitor employed in the practice of the invention will generally be within the range of from 2 to 10 parts by weight per parts by weight of rubber. A preferred range is 4 to 7 parts by Weight per 100 parts by weight of rubber. -While an amount in excess of 10 parts is seldom necessary, it is within the scope of the invention to increase the amount of additive as desired.

The invention is applicable to all types of rubber, both natural or synthetic. The synthetic polymers include the groups prepared by polymerizing a conjugated diene of 4 to 10 carbon atoms, either alone, or in combination with an unsaturated comonomer such as styrene, acrylonitrile, methacrylonitrile, methyl vinyl ether, methylmethacrylate, vinyl-substituted pyridines and the like. Generally, the conjugated diene, such as butadiene, isoprene, hexadiene, etc., comprises a major amount of the monomer system. The invention is also applicable to polychloroprene and rubbers of the polyurethane and isocyanate types. For a more complete discussion of the various synthetic rubbers, attention is directed to Whitby, Synthetic Rubber, published by John Wiley and Sons, Incorporated, New York, N.Y., 1954.

In additionto the radiation damage inhibitors of this invention, the rubber can be compounded with other ingredients such as reinforcing agents, fillers, pigments, vulcanization agents and accelerators, antioxidants and the like. Such ingredients are Well known and include, for example, those described in Synthetic Rubber, Whitby, John Wiley and Sons, Incorporated, New York, NY. (1954).

The radiation damage inhibitors of this invention are particularly useful in protecting vulcanized rubber against damage due to ionizing radiation, such as gamma rays and the like. Curing of the compounded rubbers, including bot-h the synthetic and natural types, is generally 200 and 400 F. for from 10 minutes to 3 hours.

Total doses of ionizing radiation of from 1 10 to 4 The stocks wereroll milled, sheeted off the mill, and cured for a finite length of time at 307 F. Variations in cure time were employed to achieve essentially the 5x10 and even higher, roentgens equivalent physical, 5 same 100 percent modulus. Tensile specimens its" wide can be tolerated by the protected rubbers of this invenand 2" long (length of test portion) were cut from the tion, depending on the amount of radiation damage insheets which were 2S-30 mils in thickness. The specihibitor employed and the degree of protection desired. mens were packed into aluminum cans which were closed, The following example sets forth specific compositions purged with helium, and irradiated in a field of gamma made according to the present invention, but obviously 10 rays from spent fuel elements from the Materials Testconsiderable variation is possible from the specific ing Reactor at Arco, Idaho, at a canal temperature of amounts set forth in the examples. In said examples, approximately 75 F. A pressure of pounds helium the resistance to radiation damage imparted by a given was maintained in the cans during irradiation. Runs additive is measured by comparing the change in 100% were made with total dosages of 0.5 and 1X10 roentgens. modulus which occur in samples with and without the 15 One sheet of samples was not irradiated but was reserved additive. for control purposes. The irradiated materials were re- EXAMPLE I moved from the gamma ray field and physical properties A 75/25 butadiene/styrene rubber was prepared by were determined. The results of these tests are exemulsion polymerization at 41 F. to give a polymer havpressed as Table I.

TABLE I Parts of Cure time Radiation 100% Tensile Elon- Anti-rad employed anti-rad per at 307 F., dosage modulus strength gation 100 parts minutes (megarep.) (p.s.i.) (p.s.i.) (percent) rubber dione 5 300 o 310 3, 400 630 trans-1,4 diphenyl-2-butene-l,

lone 5 300 50 860 3, 310 290 trans-1,4-diphenyl-2-butene-1,

4dione 5 300 100 1,540 3,210 180 Diallyl phthalate 5 45 0 300 3, 280 560 Do 5 45 50 910 s, 160 250 s 45 100 1, 450 2, 860 170 ing a low Mooney value (ML-4 at 212 F.) of 52 and a It is evident from the above tabulated data that the bound styrene content of 23 percent. A recipe for the rubber containing the anti-rads of this invention was not production of such apolymer is: crosslinkecl nearly so much as that rubber which did not contain a radiation damage inhibitor. This is particu- Polymenzarwn recipe larly evident in the figures for 100% modules. Cross- Iflgfedient? Parts y Welght linking causes an increase in the modulus, and each of l,3-butadiene 75 these rubbers had a 100% modulus before radiation of Styrene 25 approximately the same value. After irradiation with Water 180 1 10 roentgens equivalent physical (100 megarep.) a Rosin soap, K Salt much higher 100% modulus was shown by the rubber Tamol N* containing no radiation damage inhibitor than either of 7 Na PO 'l2H O the inhibitor-containing rubbers. The rubber containing p-Menthane hydroperoXid 7 the diallyl pht-halate was somewhat superior to the rubber FeSO '7I-I O containing the dione, while both were much superior to K P Oq the control. Tfi y mefCaPtaI1aS quired for a 52 While certain embodiments of the invention have been ML-4 polymer. described for illustrative purposes, the invention obvirsgdium lt'of a naphthalene sulfonic acid condensed with 55 ously is not limited thereto. Various other modifications formaldehyde. will be apparent to those skilled in the art in view of this The above prcpared bb was compounded ith the disclosure. Such modifications are within the spirit and desired radiation damage inhibitor, and a control was run cope the nv n which contained no inhibitor. The compounding recipe I claim: employed was as follows: 1. A method of making a rubbery polymer selected from the group consisting of conjugated dienes and co- Compmmdmg recipe polymers of conjugated dienes and vinyl substituted aro- Ingredient: Parts by weight matics stable to ionizing radiation which comprises the Butadiene/styrene rubber 100 steps of: (1) incorporating in said rubber during the C b bl k 5O compounding thereof, as a radiation damage inhibitor, Zi id 3 at least one compound selected from the group of com- Stearic acid 1 pounds having the structural formulas: Antioxidant 17. 5 g u Sulfur I Vulcanization accelerator 1 2 2 and RioR@-o n, Radiation damage inhibitor 5 wherein R is selected from the group consisting of rum 119mm k0 hi h brasion furnace black matic and substituted aromatic nuclei containing from a A i containing 65 weight pare-ant of a 6-20 carbon atoms, sa d aromatlc nuclei belng selected complex diarylamine-ketoue reaction product and 30 percent f th group Conslstmg f benzene nucleus, h h weight M NN"diphenyl'p'phenylenediamme' lene nucleus and biphenyl nucleus, and the substituents of said substituted aromatic nuclei being selected from the group of radicals consisting of alkyl, amino, car-boxy and acyl, R is an :alkenyl radical containing from 2-6 carbon atoms, and R is an alkenylene radical containing from 2-6 carbon atoms; (2) vnlcanizing the composition; and (3) thereafter exposing the composition to ionizing radiation of from 1x10 to 5 10 roentgens.

2. The method of claim 1 wherein said radiation damage inhibitor is added in an amount being in the range of 4-7 parts by weight for each 100 parts by weight of said rubber.

3. The method of claim 1 wherein said radiation damage inhibitor is diallyl phthalate.

4. The method of claim 1 wherein said radiation damage inhibitor is trans-1,4-diphenyl-2-butene-1,4-dione.

5. The method of claim 1 wherein the rubber material is a copolymer of butadiene and styrene.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Institution of the Rubber Industry Transactions, De polymerized Rubber-Monomer Compositions, vol. No. 2, pp. 6372, April 1959.

LEON J. BERCOVITZ, Primary Examiner.

ALFONSO D. SULLIVAN, MILTON STERMAN,

Examiners.

H. LEVINE, J. W. WILLIAMS, G. W. RAUCHFUSS,

Assistant Examiners. 

1. A METHOD OF MAKING A RUBBERY POLYMER SELECTED FROM THE GROUP CONSISTING OF CONJUGATED DIENES AND COPOLYMERS OF CONJUGATED DIENES AND VINYL SUBSTITUTED AROMATICS STABLE TO IONIZING RADIATION WHICH COMPRISES THE STEPS OF: (1) INCORPORATING IN SAID RUBBER DURING THE COMPOUNDING THEROF, AS A RADIATION DAMAGE INHIBITOR, AT LEAST ONE COMPOUND SELECTED FROM THE GROUP OF COMPOUNDS HAVING THE STRUCTURAL FORMULAS: 